Strange sum (riddle tread)
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26-01-2012, 09:54 AM
RE: Strange sum (riddle tread)
1.5?



....

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26-01-2012, 10:00 AM
RE: Strange sum (riddle tread)
(26-01-2012 09:54 AM)Stark Raving Wrote:  1.5?

No,

|1.5+2| +|1.5-3| = |3.5| +|-1.5| = 3.5 + 1.5 = 5

The "|" sign in math means "absolute value" which is always positive.
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26-01-2012, 10:40 AM
RE: Strange sum (riddle tread)
Puzzles FTW Big Grin

Hmm, seems like the minimum answer for the equation |x+a| +|x-b| will be (a+b), in the case of this equation |x+2| +|x-3| = 2, the supposed minimum answer is 5.

Here's my take:
Convert all the | to 1,
1x + 21 + 1x -31 = 2
x + 21 + x - 31 = 2
2x - 10 = 2
2x = 12
x=6

I think there is another approach to this question Smile Will figure it out later Tongue

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26-01-2012, 11:12 AM
RE: Strange sum (riddle tread)
Still no, I am afraid.

The definition of the absolute value function is the following:

|y| = y if y>=0

|y| = -y if y<0

examples:

|145| = +145

|-37| = +37

|0| = 0

Use these definitions to check your suggested results. Tongue
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26-01-2012, 11:52 AM
RE: Strange sum (riddle tread)
(26-01-2012 10:00 AM)Zat Wrote:  |1.5+2| +|1.5-3| = |3.5| +|-1.5| = 3.5 + 1.5 = 5

Where did you get the third 1.5 from in that answer?

X(1.5)+2=3.5
X(1.5)-3=-1.5
3.5+ -1.5= 2
X=1.5

I have the feeling I've over looked something as stark gave the same answer as me and you said it was wrong. But as far as I can tell my calculations fit.

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26-01-2012, 12:05 PM (This post was last modified: 26-01-2012 12:13 PM by Zat.)
RE: Strange sum (riddle tread)
(26-01-2012 11:52 AM)FSM_scot Wrote:  
(26-01-2012 10:00 AM)Zat Wrote:  |1.5+2| +|1.5-3| = |3.5| +|-1.5| = 3.5 + 1.5 = 5
Where did you get the third 1.5 from in that answer?

1.5-3 = -1.5 (plus one and a half minus 3 equals minus one and a half)

As I showed in my previous post: the absolute value function ALWAYS returns the positive version of the number it is applied to:

so

|-1.5| = +1.5

PS. The |x| notation in math is not the same as the round brackets (x). It is a function that always returns the positive value of the number between the two "|" signs.
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26-01-2012, 12:33 PM
RE: Strange sum (riddle tread)
I see. So there can be no negative numbers anywhere when working it out as they must be positive? (maths isn't my strong point)

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26-01-2012, 12:47 PM
RE: Strange sum (riddle tread)
(26-01-2012 12:33 PM)FSM_scot Wrote:  I see. So there can be no negative numbers anywhere when working it out as they must be positive? (maths isn't my strong point)

For those of you who are ready to give up I posted the solution in the riddle-solutions thread.
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26-01-2012, 02:41 PM
RE: Strange sum (riddle tread)
moah you guys are too fast for me. I am bad at maths. I just had to ask a physist friend of mine to explain to me what the whole thing means. and now i wanted to start solving it but someone was faster. not fair. *starts crying like a child*
Post something I can solve without calculating and having to know maths plox

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26-01-2012, 02:58 PM
RE: Strange sum (riddle tread)
(26-01-2012 09:49 AM)Zat Wrote:  |x+2| +|x-3| = 2

Taking a stab: I think there's no answer. i.e. no real x which satisfies the above. Now I check answers thread. Hope I got it right Confused I studied maths at uni Tongue
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